Molecular characterization of carbapenemases production among environmental Gram-negative isolates at Addis Ababa, Ethiopia: first detection of NDM Producers in hospital environments

J Infect Dev Ctries. 2025 Apr 29;19(4):512-519. doi: 10.3855/jidc.20561.

Abstract

Introduction: The Gram-Negative bacteria, particularly carbapenem-resistant strains (CR-GNB), pose a global health threat due to high morbidity and mortality. Detecting carbapenemase-encoding genes is essential for understanding their spread in hospital environments. This study investigated environmental colonization by CR-GNB in Ethiopian hospitals, including genetic characterization of resistance genes.

Methodology: A cross-sectional study analyzed 103 environmental GNB isolates collected from inanimate surfaces at Tikur Anbessa Specialized Hospital (TASH) and ALERT Hospital (June-September 2021). Conventional microbiological methods identified the isolates, and antimicrobial susceptibility was tested using the Kirby-Bauer disk diffusion method. Carbapenemase production was screened using the Modified Hodge test (MHT) and combined disk test (CDT). Resistance genes (blaKPC, blaNDM, blaOXA-48) were detected via PCR in isolates with reduced meropenem susceptibility.

Results: The predominant GNB were Acinetobacter baumannii (47%), Pseudomonas aeruginosa (33%), and E. coli (12%). Among 103 isolates, 62% showed reduced meropenem susceptibility. The most common CR-GNB was Acinetobacter baumannii (37.5%), followed by E. coli (18.8%) and Klebsiella pneumoniae (12.5%). Carbapenemase production was detected in 41.7% of isolates via PCR, with blaNDM being the most common (43 isolates). Linens (26.4%) and beds (21.4%) had the highest contamination rates. Most carbapenemase-producing isolates were multidrug-resistant (MDR).

Conclusions: The presence of blaNDM and blaKPC genes highlights hospital surfaces as reservoirs for resistance genes, contributing to healthcare-associated infections. Routine surveillance and early detection of carbapenemase producers are crucial for infection control and antimicrobial resistance management.

Keywords: Carbapenem-resistance; MDR; carbapenemase; multidrug-resistant; β-lactamase.

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Bacterial Proteins* / genetics
  • Cross-Sectional Studies
  • Environmental Microbiology*
  • Ethiopia
  • Gram-Negative Bacteria* / drug effects
  • Gram-Negative Bacteria* / enzymology
  • Gram-Negative Bacteria* / genetics
  • Gram-Negative Bacteria* / isolation & purification
  • Hospitals
  • Humans
  • Microbial Sensitivity Tests
  • beta-Lactamases* / genetics

Substances

  • beta-Lactamases
  • carbapenemase
  • Bacterial Proteins
  • Anti-Bacterial Agents